The optical system of the human eye uses numerous muscles as well as central and peripheral cues while focusing on objects both near and far. There are many responses involved in changing focus from distance to near as well as fixating on an object at a set distance.
While focusing on near objects, such as a computer, the visual system must converge on the object being viewed. After a period of time the eyes may become strained, feel dry, or start to blur. It is believed that the visual system after prolonged near activity may experience a proprioceptive lag as to where the object being viewed is located. In other words the perceived distance of the object being viewed is different than its actual location. When this occurs the visual system in many instances develops eye strain due to the constant cortical supervision to maintain binocularity. Fatigue, eyestrain, dry eye, along with other symptoms are the results of the misalignment or eyes.
While the use of this system and method is intended to be used with any ophthalmic lens, it is particularly relevant to the ophthalmic lenses described in U.S. Pat. No. 7,104,647, “Multi-focal ophthalmic lens with base in prism”. This invention is intended to compliment U.S. Pat. No. 7,104,647 by determining if additional prism is needed for the distance portion of the ophthalmic lens.